The object of this research project is to study the molecular biology of prothrombin synthesis and the role of vitamin K and the coumarin-anticoagulant drugs in its regulation. It is now established that the site of action of vitamin K and the coumarin-anticoagulant drugs is a post-translational carboxylation of peptide-bound glutamate residues in the N-terminal portion of a prothrombin precursor. The goals of this project are: (1) to purify the vitamin K-dependent carboxylase to homogeneity; (2) to isolate and identify intermediated of vitamin K in the vitamin K-dependent carboxylation by HPLC, GLC, and mass spectrometry; (3) to sequence the mRNA translation product and the pI 7.2 form of prothrombin precursor for microsomes; and (4) to demonstrate an inhibitory activity of the warfarin-binding protein on the carboxylation in vitro.